Wild Mushroom Potato Gratin

Recipe from Gourmet Magazine September 2003 and Husband-Tested in Alice's Kitchen
Makes 8 servings

This mild, wet weather has brought us a fabulous array of mushrooms in our woods. Right now, my husband Jim is bringing home bags of chanterelle mushrooms that he has foraged. Lost River Market & Deli has had some as well in their produce section recently brought in by a local forager. We've sauteed most of our mushrooms in a bit of unsalted butter and put them in the freezer for later as recommended by my Internet research. Jim has been thawing them and putting them in his pasta. I made this dish for our friends Bob and Debbie using fresh chanterelles from our woods, crimini mushrooms from Lost River Market & Deli and Simon's potatoes from the Orange County HomeGrown Farmers Market. This was so yummy, I'm planning to use some of the frozen mushrooms later this fall maybe for a Thanksgiving get together. It'll be a big hit!

1/2 lb fresh wild or exotic mushrooms such as chanterelles or shiitakes (discard shiitake stems), trimmed and coarsely chopped
2 1/2 tablespoons unsalted butter
3/4 lb fresh cremini mushrooms, trimmed and sliced 1/4 inch thick
1 1/2 teaspoons minced garlic
3 lb russet (baking) potatoes
1 1/2 cups heavy cream
1 1/2 cups whole milk
1 1/2 teaspoons salt
1/2 teaspoon white pepper
1/4 teaspoon freshly grated nutmeg
2 oz finely grated Gruyère (1 cup)

Put oven rack in middle position and preheat to 400°F.
Cook chanterelles or shiitakes with salt and pepper to taste in 1 tablespoon butter in a large nonstick skillet over moderate heat, stirring, until liquid mushrooms give off is evaporated and mushrooms are tender, about 8 minutes, then transfer to a bowl. Cook cremini in remaining 1 1/2 tablespoons butter in skillet, stirring, until liquid is evaporated and mushrooms are tender, about 8 minutes, then transfer to bowl with wild mushrooms. Toss mushrooms with 1 teaspoon garlic.
Peel potatoes and cut crosswise into 1/8-inch-thick slices (preferably with an adjustable-blade slicer). Bring potatoes, cream, milk, salt, white pepper, nutmeg, and remaining 1/2 teaspoon garlic to a boil in a 4- to 6-quart heavy pot, stirring once or twice, then remove from heat.
Transfer half of potatoes to buttered gratin dish with a slotted spoon, spreading evenly. Spread mushrooms evenly over potatoes, then top with remaining potatoes. Pour cooking liquid over potatoes and sprinkle with cheese.
Bake gratin until top is golden brown and potatoes are tender, 45 to 55 minutes. Let stand 10 minutes before serving.
Cooks' note: •Instead of using 1/2 lb of 1 type of wild or exotic mushroom, you could use 1/4 lb each of 2 types.